TABLE 2.

Serum and tissue retinol concentrations and total tissue amount in rats fed 3 different amounts of dietary niacin and receiving 3 different daily doses of retinyl acetate¹

Treatment2	Serum retinol (μmol/L)	Serum total retinyl ester (μmol/L)	Percentage retinyl ester of serum total VA	Liver retinol (μmol/g)	Liver total retinol (μmol)3	Small intestine (nmol/g)	Small intestine total retinol (nmol)3
Baseline	2.05 ± 0.09	0.02 ± 0.00	0.92 ± 0.21	0.09 ± 0.01	0.69 ± 0.08	0.91 ± 0.33	4.69 ± 2.32
50 nmol
0 mg/kg	1.04 ± 0.15d,†	0.06 ± 0.05c	5.23 ± 4.30d	0.22 ± 0.04e	0.76 ± 0.16f	2.15 ± 1.51cd	8.61 ± 5.61c
15 mg/kg	2.12 ± 0.26a	0.02 ± 0.01c	1.15 ± 0.51d	0.15 ± 0.05f	0.81 ± 0.13f	1.18 ± 0.28d	6.54 ± 1.34c
30 mg/kg	2.59 ± 0.40a	0.03 ± 0.01bc	1.12 ± 0.15d	0.08 ± 0.01g	0.80 ± 0.07f	0.96 ± 0.21d	5.93 ± 1.26c
350 nmol
0 mg/kg	1.19 ± 0.32cd,†	0.05 ± 0.02b	4.18 ± 1.94c	0.98 ± 0.11c,†	3.66 ± 0.81e	4.97 ± 1.90bc	22.9 ± 9.35c
15 mg/kg	1.89 ± 0.39b	0.04 ± 0.02bc	2.30 ± 1.25d	0.92 ± 0.05c,†	4.98 ± 0.92d	12.6 ± 7.58b	61.3 ± 41.3c
30 mg/kg	2.31 ± 0.13a	0.05 ± 0.02bc	2.00 ± 0.80d	0.60 ± 0.05d	5.67 ± 0.32c	6.33 ± 1.35b	39.6 ± 9.03c
3500 nmol
0 mg/kg	1.51 ± 0.38bc	0.62 ± 0.26a,†	39.4 ± 9.93a,†	9.18 ± 0.73a,†	36.3 ± 8.42b,†	188 ± 79.3a,†	859 ± 341b,†
15 mg/kg	2.32 ± 0.35a	0.41 ± 0.12a,†	18.4 ± 6.31b,†	8.75 ± 0.70a,†	41.4 ± 6.34b,†	229 ± 53.4a,†	1230 ± 286ab,†
30 mg/kg	2.70 ± 0.62a,†	0.62 ± 0.31a,†	21.8 ± 7.06b,†	5.39 ± 0.63b,†	52.3 ± 6.21a,†	287 ± 121a,†	1700 ± 672a,†
P4
Niacin	<0.0001	0.042	<0.0001	<0.0001	<0.0001	NS	0.07
VA	<0.0001	<0.0001	<0.0001	<0.0001	<0.0001	<0.0001	<0.0001
Interaction	0.01	0.013	<0.0001	<0.0001	<0.0001	0.024	0.038

¹All values are mean ± standard deviation. Differing letters in columns indicate significance at P < 0.05 determined by 2-factor ANOVA (excluding baseline) with LSMEANS and TUKEY-KRAMER correction. ^†Significance at P < 0.05 compared with baseline values determined by 1-factor ANOVA with LSMEANS and Dunnet correction.

²Treatments are 3 amounts of VA dosage (50, 350, and 3500 nmol/d) by 3 different amounts of dietary niacin (0, 15, and 30 mg/kg) in a 3 × 3 design.

³Total retinol calculated by multiplying retinol concentration by organ weight for each rat. Liver and small intestine weight were significantly affected by niacin treatment (Table 1).

⁴Treatment effect P values are from a 2-factor ANOVA that does not include the baseline group.